A Versatile Programmable Flow Injection Platform for Shipboard and Autonomous Analysis of Nutrients and Trace Metals

The supply and concentration of nutrients and trace metals exert a fundamental control on marine productivity, phytoplankton community structure, and carbon cycling in the ocean. High-quality measurements of nutrients and trace metals are essential for understanding these processes that govern life in the ocean. However, most wet-chemical methods remain difficult to operate during extended shipboard campaigns and are unsuitable for unattended deployment. As a result, established methods for trace metals and nutrients other than nitrate have not kept pace with the expansion of autonomous ocean observing platforms. Building on prior NSF support that established programmable Flow Injection (pFI) for nutrients and dissolved aluminum analysis, this project will expand U.S. capability in trace metal oceanography and advance the pFI platform toward the more difficult measurement of iron. The project will train graduate and undergraduate students in wet-chemical instrumentation, method development, uncertainty analysis, and data interpretation. Public demonstrations will engage the community in coastal observing and ocean health monitoring. Investigators will develop and validate a shipboard method for sub-nanomolar dissolved iron and assess its suitability for autonomous operation in a coastal setting. In parallel, they will deploy an autonomous pFI analyzer at the Moss Landing shore station to produce an 18-month long hourly record of phosphate and silicate co-located with an existing UV nitrate sensor. The project will advance chemical oceanographic measurement by transforming wet-chemical analysis from dispersion-based continuous flow systems to programmable reaction-zone control. Adapting pFI to dissolved iron will establish a robust, sub-nanomolar shipboard method within a universal fluidic manifold capable of supporting kinetically distinct trace metal assays. Long-duration coastal deployments will quantify analytical stability and combined measurement uncertainty under sustained field operation, providing performance benchmarks required for future autonomous chemical sensing applications. The sustained phosphate–silicate time series will provide high-frequency observations of cross-shelf exchange along a steep continental margin, where internal tides and bores transport nutrient-rich deep waters onto the shelf. Resolving variability at tidal-to-seasonal timescales will clarify how offshore source waters and nearshore modification interact to structure nutrient stoichiometry in productive coastal environments. Together, these advances will move wet-chemical oceanographic measurements from expert-operated shipboard methods toward sustained autonomous chemical observing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.